MPGe -vs- MPD : The Real Figure of Merit? One thing I’ve not seen focused on regarding the Tesla Model S, and electric vehicles in general, is the actual cost of fuel… in this case electricity, as compared to gasoline. I call this “Miles Per Dollar”, or MPD for short. You can sometimes find this data, but often you have to derive it, because, as with other fuels, price varies with location… often significantly. What is more commonly found is “MPGe”, which is the EPA’s attempt to quantify how efficient a vehicle is in using the equivalent amount of energy from a gallon of gasoline. Unfortunately, because it doesn’t factor cost in to the equation (and rightly so, as mentioned above it would be hard to do so), I believe it gives people a false impression. For example, the Model S has an MPGe rating of 95. For the casual observer, they will assume that the Model S “gets about 2-3 times the mileage of a good economy petroleum-fueled car”. What that fails to account for is that THE COST TO ACQUIRE THE EQUIVALENT FUEL IS DRAMTICALLY LOWER IN JUST ABOUT EVERY CIRCUMSTANCE. This generality is based on the fact that, although electricity costs vary, the places with higher electrical costs also generally have higher fuel costs. So while it might take 2-3 gallons of gas (or diesel) to go 97 miles in the economy car , and only one gallon’s equivalent amount of electricity in the Model S, it will cost eight to twelve dollars (@$4/gal) versus three to four-and-a-half dollars (@ 10-15 cents/KWh). My own example: My Toyota 4Runner got 19 MPG. The Model S is rated at 5 times that (95 MPGe). You would expect it to then be 5 times less expensive to operate. Yet (for me) it’s much less. Driving the 4Runner 19 miles will consume 1 gallon of gas, costing me $4. Driving my Model S 19 miles will consume about 6KWh of energy, which with my state’s EV Time of Usage (ToU) metering plan of $0.055/KWh will cost me $0.33 That’s TWELVE times less fuel cost. Now of course, everybody’s costs vary, and that’s why it’s hard to slap a single rating on the car. I suspect, however, that for many (most?) folks the MPD is even more attractive than the MPGe rating would imply at first glance. And how much of a factor that makes in the value proposition depends on an individual’s driving habits, what type of vehicle they are transitioning from, etc... But when I talk to people, I’m sure point out what the energy costs are so they can see the value in considering it along with the other factors that drive the total cost of ownership.